Potassium oxide

Crystal structure
__ K +      __ O 2−
General
Surname	Potassium oxide
other names	Dipotassium oxide Potassium monoxide POTASSIUM OXIDE ( INCI )
Ratio formula	K 2 O
Brief description	hygroscopic, colorless and odorless crystals
External identifiers / databases
CAS number 12136-45-7 EC number 235-227-6 ECHA InfoCard 100.032.012 PubChem 9989219 ChemSpider 8164801 Wikidata Q408880
properties
Molar mass	94,20 g · mol -1
Physical state	firmly
density	2.32 g cm −3
Melting point	> 740 ° C decomposes at 350 ° C
solubility	violent decomposition in water
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 314 P: 101-102-280-303 + 361 + 353-305 + 351 + 338-405
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Potassium oxide (K ₂ O) is a chemical compound from the group of alkali metal oxides and is a white solid.

Extraction and presentation

Potassium oxide can be obtained through the reaction of oxygen and potassium , whereby potassium peroxide K ₂ O ₂ and, through the reaction with further potassium, then potassium oxide is formed.

${\displaystyle {\ce {K2O2 + 2K -> 2K2O}}}$

Alternatively, potassium oxide can be created by heating potassium nitrate with potassium:

${\displaystyle {\ce {2KNO3 + 10K -> 6K2O + N2}}}$

properties

Physical Properties

Potassium oxide has a antifluorite - crystal structure . In this structure, the anions and cations exchange their positions compared to that of calcium fluoride .

The standard enthalpy of formation of potassium oxide is ΔH _f ⁰  = −363 kJ / mol.

Chemical properties

Like other alkali metal oxides, potassium oxide forms a hydroxide on contact with water , in this case potassium hydroxide (KOH), which dissolves in water to form potassium hydroxide .

${\displaystyle {\ce {K2O + H2O -> 2KOH}}}$

Potassium oxide is the anhydride in potassium hydroxide. In the air it reacts with the humidity to form potassium hydroxide and with carbon dioxide to form potassium carbonate .

${\displaystyle {\ce {2KOH + CO2 -> K2CO3 + H2O}}}$

Potash lye is a strong lye that, like caustic soda , attacks fats , base metals and glass , among other things . With strong acids , rapid, sometimes vigorous neutralization occurs . The reaction is slower with weak or very dilute acids . It formed potassium salts .

use

Potassium oxide itself is not used as a fertilizer (PK / NPK fertilizer), but is used there as a unit of measurement for the proportion of potassium (e.g. in the form of potassium sulfate , potassium formate , potassium nitrate or potassium chloride ) in the fertilizer.

See also

• Potassium peroxide
• Potassium hyperoxide

Individual evidence

1. ↑ Entry on POTASSIUM OXIDE in the CosIng database of the EU Commission, accessed on March 4, 2020.
2. ↑ ^{a b c d e f} Entry on potassium oxide in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .
3. ^ AF Holleman , N. Wiberg : Inorganische Chemie . 103rd edition. Volume 1: Basics and main group elements. Walter de Gruyter, Berlin / Boston 2016, ISBN 978-3-11-049585-0 , p. 1515 (reading sample: Part A - Basics of the chemistry of hydrogen. Google book search ).
4. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , p. 1285.
5. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , p. 1286.
6. ↑ Federal Ministry of Justice: Ordinance on the placing on the market of fertilizers, soil additives, growing media and plant additives (Fertilizer Ordinance - DüMV) §6 (definition of fertilizer types)